Ear plug and sound absorbing material construction



March 23, 1954 c. LEIGHT 2,672,863

EAR PLUG AND SOUND ABSORBING MATERIAL CONSTRUCTION Filed May 29,' 1951removal of the plug from the ear canal.

Patented Mar. 23, 1954 UNlTED STATES PATENT OFFICE EAR PLUG AND SOUNDABSORBING MATERIAL CONSTRUCTION Charles Leight, Los Angeles, Calif.

Application May 29, 1951, Serial No. 228,851

2 Claims. 1 Thisvinvention relates to sound absorbing devices, andparticularly to an ear plug adapted to decrease or attenuate theamplitude of sound waves reaching the ear drum of a person.

The use of ear plugs to prevent auditory injury and noise fatigue arewell-known, and plugs for attenuating the amplitude of sound wavesreaching the ear have been used in different occupations. Ear plugs arealso worn by aviators, in which case the plugs should be of a type whichare comfortable when worn under headphones.

The construction of the present plug is of the general type disclosedand claimed in my U". S. Patent No. 2,446,707.01 August 10, 1948. Thisprior plug is in the form of a cylindrical body tapered at one end andhaving a right-angle handle section to facilitate the insertion and Thepresent plug has two general over-all shapes.

One is of the type shown in the above mentioned patent, and the other isone whereby the external form is modified for improving the fit of theplug in the ear.

The primary feature of the present plug is a filler insert made of aspecial formula spongy sound absorbing material to improve the selectiveabsorptivity of the sound waves. The insert may be in two sections, asshown in the patent, or may be a single unit. The plug is provided withpressure equalizing vents and an opening which aids the transmission ofthe lower frequencies to permit almost normal conversation whileprotecting the ear from harmful noise amplitudes and frequencies.

The principal object of the invention, therefore, is to facilitate theselective attenuation of sound amplitudes and frequencies to the ear.

Another object of the invention is to facilitate the fit of a soundabsorbing ear plug in the ear.

A further object of the invention is to provide an improved ear plugwhich absorbs the harmful noise while permitting the plug to be wornunder earphones.

A still further object of the invention is to provide an improved methodof constructing an ear plug which is comfortable in the ear at all timesand which is particularly efficient in the absorption of harmful soundwaves while permitting almost normal conversation.

A still further object of the invention is to provide an improved methodof producing a selective sound absorber for ear plugs.

A still further object of the invention is to pro- Although the novelfeatures which are believed to be characteristic of this invention willbe pointed out with particularity in the appended claims, the manner ofits organization and the mode of its operation will be better understoodby referring to the following description, read in conjunction with theaccompanying drawings, forming a part hereof, in which:

Fig. 1 is a perspective view of one form of ear plug embodying theinvention.

Fig. 2 is a sectional view, partly in cross-section, of the plug shownin Fig. 1.

3 is an expanded view of the plug shown in Figs. 1 and 2 showing theselective sound absorbing insert.

Fig. 4 is a perspective view of a second modification of an ear plugembodying the invention, and

Fig. 5 is a sectional view, partly in cross-section, of the ear plug ofFig. 4.

Referring now to the drawings, in which the same numerals identify likeelements, the plug is vide an improved sound absorber for ear plugs.

formed of a thin outer shell or skin 5 of flexible material, such assheet rubber, obtained by molding, the tip of the plug having pressureequalizing vents 6. Molded to the skin section 5 and as an integral partthereof is a handle formed with a section 1 at right angles to thelongitudinal axis of the plug, and a section 8 at right angles tosection I and parallel to the longitudinal axis of the plug. The section1 is tapered from opposite points on the circumference of the largerdiameter section of the skin section 5 to the width of the rectangulartab section 8.

As shown in Figs. 1, 2, and 3, one end of the plug is pointed in an ovalor bullet shape, while the skin section is of two diameters, the sectionI0 having the point formed at one end thereof.

Section in is of a smaller diameter than the section II, the variationin diameters being approximately one-sixteenth of an inch. That is, thesmaller section ID for a medium sized plug is approximatelysix-sixteenths of an inch in. diameter, and the diameter of the largersection. II is approximately seven-sixteenths of an inch. For othersizes of plugs, these dimensions areproportional. The length of the tabsection 1 for a plug having the above dimensions is oneeighth of aninch, and the length of the section 8 is three-sixteenths of an inch. Atwo-sectioned plug of this type has been found to be easily insertableand removable from the ear, while providing a snug fit to prevent thepassage of sound waves around the plug.

Referring now to the plug shown in Figs. 4 and 5, this plug has a skinsection I4 of the same type as the skin section 5 of the firstmodification, and also, has the same form of integral tab with sectionsI5 and I6; It also has equalizing vents H. Th diiference between theplugs in Fig. 1 and in Fig. 4 is in the shape of the skin section [4. Ithas been found that the ear canal is such that a betterfit fonmany earcanals is-generally accomplish d the. sla eer diameter s ct on" lsimilar to section II in Fig. 1, extends only one- That is, one-half ofthe plug divided lengthwise is cylindrical from th open end 0f-'- thetskin leto the point, while the other half varies in diameter 20, andthen baked at a temperature of substantially 250 degrees Fahrenheit forapproximately eighteen minutes. This time has been varied betweenfifteen and twenty-five minutes with satisfactory results. After theinserts are cured, they are punched from the mold. Although cellulcse ispreferred, finely ground cork has been usedwith satisfactory-results.

vrizf heaaboveeear plugsgitheretorei *are particu- 10 larly efficient inabsorbing an adequate proporhalf way around the circumference of theplug I tion of harmful noise to reduce the noise level to a safe value.The ear plugs are safe, comfort- -,able,g; and invisible, and may beworn with com- "fortat work or during sleep. Ventilation is prosimilarlyto the plug of Fig. 1. Thatis section e 5 videdtqlthe inner ear to avoiddizziness, and the IQ divided transversely is the same as section in ofthe plug in Fig. 1, while section-118 is onl-y onehalf of section II.This provides an improved. wedging action, inasmuch as the tab is alwaysplaced toward the backof the ear.

The primary improvement of;th ;p lugs above described is provided-by-theuse of a ,newform of absorbent filler insert shown atin. both plugs;This material is molded'to-fitthe internal form of either skin 5- 0r-l4,the form-forFig. 1 being shown in perspective in Fig. 3.; Theginsert :20has ahole 2| therein extending"axiallyofthe plug for a short distance;therein."- Thisopening has been found'to aid-'the-passage of the lowerfrequencies to the ear -drum, and thus, permit almost normalconversation while 'the" plugs are being worn, theplugsattenuatingthe;higher;amplitude levels-andfrequencies of the soundwaves. This opening, along Withvents 6; aids in; pressure equalizationas well as permitting f-breathing" -of the plug for ventilation.

The plug- 20- is made fromdatex foamrubber impregnated with flocculatedcellulose. To -produce the soundabsorbing-insert 20; the latex foam maybe made in'accordance-with several standard formulas. The formula usedherein consists of approximately sixty-five;-percent of dry latex byweight-to approximately "thirty flve percent of other-ingredients. Theseother-im ingredients are a soap solution to produceemulsi- :7ficationand frothing, accelerators and sulfur for curing orvulcanization, a protective colloid for stabilization, an=anti-oxidantfor optimum aging, a metallic salt-to activate curing,-a-colorcarrier -=to provide the desired opacity,-a color-pigment, and agellation material to control-coagulation of the-foam.

solution is mechanically mixed with? the 'r flocculated cellulose-at theratio'of' on hundred parts of the dry latex rubber component-to three totwenty parts ofcelluloseby weight. After the liquid--latex foam andcellulose are thoroughly .mixed, themixture is poured into adie-of"-;the

. proper shape to form an insertsuch as shown at plugs are shaped toprovide a beveled wedging -=action insuring=- one hundred percenteiiiciency ,atifillvtimes. The special type of insert material has beenfound to have the ability to absorb the 20 higher frequencies of soundwaves, I while xpermitting' the lower frequencies f conversatiOn to Ipenetrate to; the ear." Therefore it is unnecesyt m ve t e uss f rnormal convers tion.

e a me -m d ma. fo m. tb t t a ticular internal shape of the skin orshellportion of ,1 the plug. The: inserts generally remain fixed intheir shells after insertion, buta spot 'of glue may be a plied at, the;time, Of insertion;to

36 insure their remaininginposition.

I claim:

, 1. In an ear devicehaving a shelLanjnsert j plug comprising i asolidintegral member formed -;-o f a-vulcanized mixtur of liquid latex foam;and

-;-cel1ulose, said member beingshapedto'fitithe -i-nterioriof the shell.

'- 2; In a plugffor-an:eardevice, a solid'-integral member havinglatexfoam and cellulose mixed so as to absorb soundwavesof-relativelybh'igh 0 frequeneieswhile permitting the passage" 'jofsound waves of lower "frequencies," said member being provided with anaxially extending hole for ventilating the plug.

- CHARLESIIJIEIG'HT.

References: Cited iinthe :file- *of this patent "U ITED STATESFATENTIfi"Name 7 Number ,135,9 2

, cgeaqov 2,498,785

.12.568366. 0sterhof,Leanne. .,m, f.

FQREIGN PATENTS Num e Cou try Date iv 1,387 1. GreatBritam b11888

